invention relates to a process and device for the virtually continuous filling of fiber structure electrode plaques for accumulators with an active compound paste under the action of vibrations, the plaques being provided with current discharge lugs.
Electrodes for voltaic cells can be produced by filling a porous electrode plaque, e.g. a metal or metallized plastics foam or a metal fiber structure plaque or a metallized plastics fiber structure plaque, with active fillers including an active compound. In order to facilitate and complete the introduction of the active compound into the pores of the plaque, mechanical or physical aids such as rollers, doctor blades, as well as the action of vibrations, in particular ultrasound, are used.
A process for depositing disperse substances in porous bodies is described in German Patent Specification 1,210,417 wherein an ultrasonic vibrator is covered with a disperse substance made up into a paste of viscous consistency, the porous body is laid on top of the vibrator, covered with a layer of disperse substance of the same consistency as that covering the vibrator and, with simultaneous ultrasonic excitation, the porous body is pressed against the ultrasonic vibrator. As soon as the ultrasonic vibrations are switched off, the filled body is removed from the device. This process is exceptionally labor intensive and hence cost intensive and there are difficulties in the removal of the filled body from the device.
U.S. Pat. No. 3,262,815 describes a continuous process for the production of battery electrodes in which a strip of steel wool is first metallized electrolytically and is then covered with a layer of a slurry of an active electrode material. The active electrode material is sucked into interspaces in the strip with the aid of an applied vacuum. The strip is then washed, dried, compressed between rollers and cut to electrode size. A current discharge element must be secured on the finished electrode, which, as experience has shown, does not produce particularly durable connections. In the disclosure of U.S. Pat. No. 3,262,815, a total of three different methods are described for filling electrode plaques and it is stated that complete filling of the plaque cannot be achieved by one method alone, this indeed being indicated in addition by the compacting of the filled lattice necessary in the continuous process. In the patent, it is therefore proposed that a combination of all three methods be employed, namely immersion, covering with a layer and mechanical working-in. Nevertheless, it is not possible even with this combined filling method to dispense with the compacting of the filled plaque. Thus, because of the large number of treatment steps, this process too is quite expensive.
It is an object of the invention to provide a simple process and a device for filling fiber structure electrode plaques provided with welded-on current discharge lugs which can be carried out simply, inexpensively and rapidly and can proceed largely automatically.
In the process and the device, an unfilled fiber structure electrode plaque is first secured by its current discharge lug in a transport device. This transport device can comprise a chain conveyor or a carousel conveying device. The work carrier of the transport device is designed such that various formats of fiber structure electrode plaques can be secured without the need to change the work carrier and so that the electrode plaque cannot slip out during transport. The securing of the fiber structure electrode plaques in the transport device can be accomplished both manually and by an automatic handling device.
With the aid of the transport device, the fiber structure electrode plaques are then transported in succession to individual processing stations, in which one process step, in each case, is carried out separately from the others. The electrode plaques are conveyed from one station to the next processing station at the same time. The cycle time for this transfer process can be adjusted and is preferably between about 5 sec and 25 sec.
Following the securing of the fiber structure electrode plaque on the transport device, the fiber structure electrode plaques are immersed in a filling chamber provided with active compound. During this procedure, the fiber structure electrode plaques are preferably guided by guide plates, so that they cannot touch the edge of the vessel. The active compound in the filling chamber is vibrated in order to permit easy penetration of the active compound into the pores of the fiber structure electrode plaque.
The vibrations are preferably generated by a vibrating plate, the principal extension of which is arranged substantially vertically and which is moved back and forth, in an oscillatory manner, substantially perpendicularly to a face of the fiber structure electrode plaque. The vibrating plate can be driven in a wide variety of ways, e.g. by an unbalance motor, by a rapper or an electric vibrator.
It has proven advantageous if the vibrating plate is moved towards and away from the fiber structure electrode plaque at a frequency of about 30 Hz to 100 Hz. Instead of a vibrating plate, it is also possible to employ an internal electric vibrator.
For filling, the electrode plaque to be filled is arranged substantially parallel to the vibrating plate at a distance of about 2 to 30 mm, a distance of about 5 to 15 mm being preferred. In operation, the vibrating plate moves in parallel towards the principal surface of the plaque and away from it again during transport. At maximum amplitude of the vibrating plate, the wall of the filling vessel must not be touched. An additional distance between the vibrating plate and the wall is suggested so that the active compound in the interspace between vibrating plate and wall cannot splash.
The fiber structure electrode plaque is filled as it is transported through the filling vessel or chamber provided with the active compound. The length of the filling chamber or the dwell time in the filling chamber is to be adapted depending on the time required for filling. In the case of relatively long filling chambers, it is advisable to arrange a plurality of vibrating plates in the filling chamber.
At the end of the filling chamber, the fiber structure electrode plaque filled with paste is removed from the chamber and during the removal procedure is freed from the bulk of the adhering paste on the principal surfaces of the plaque by two mutually opposite scrapers which are applied automatically. The paste stripped off drips back immediately into the filling chamber and is not lost. Lips of the scrapers are preferably produced from nickel sheet.
The fiber structure plaque then passes into a cleaning station having two brushing rollers, rotating in opposite directions, which free the faces and the long end faces of the filled fiber structure electrode plaques of residues of active compound remaining in recesses and other residues of active compound still adhering, e.g. at the transition between the plaque and the current discharge lug. For this purpose, the electrode is lowered between the rotating brushing rollers and pulled out again, or the brushing rollers are moved correspondingly over the fiber structure electrode plaque. To ensure that the brushing roller is not clogged, each of them is allocated a stripping roller which rotates with it and in addition deflects the bristles in such a way that adhering paste particles are sprayed off into a collecting housing of the brushing station. In addition, it is also possible, depending on the viscosity of the paste, the electrode thickness and the electrode format, for the brushing rollers to be rinsed with water at set intervals.
After the brushing of the side faces, the active compound is removed in a further step from edges which have not yet been cleaned. This is primarily the lower end face of the filled electrode. This end face is brushed down by a brushing roller whose axis is perpendicular to the face of the plaque. After this last cleaning step, the filled, moist electrodes can be dried, e.g. by circulating air or an infrared lamp and then removed from the transport device, or they are removed immediately and only then dried.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.